This invention relates to a non-volatile read/write memory module and more particularly to a movable non-volatile memory module for coupling to a data processing system such as a calculator for providing transportable read/write memory storage for user programs, without requiring down loading of the user program into the main memory of the data processing system.
Heretofore, transportable storage for programs has been provided by plug-in read-only memories, magnetic storage (cards or tape), or permanent non-removable read/write memory having battery backup coupled to the read/write memory within the data processing system. However, problems exist with each of these transportable mediums. The plug-in read-only memory is expensive to develop software for, and therefore required high quantity to justify the cost of the plug-in read-only memory. Additionally, user programs may not be developed in the plug-in read-only memory nor saved via the read-only memory, and thus this alternative is available only to solve a limited number of problems. Magnetic storage, such as magnetic cards or cassette, provides read-write capability, and provides a transportable storage medium for user programs, and therefore partially solves the user's problems. However, the magnetic storage medium is external to the data processing system as a whole, and therefore requires down-loading into the memory of the data processing system before it may be run. This is a slow and cumbersome process, for both storing and retrieving data by this means. The non-removable permanent read/write memory within system battery backup provides a user workspace for developing and storing programs, and retains program data so long as the read/write memory is coupled to the battery within the data processing system. Upon removal of the read/write memory from the data processing system, the data contained therein is lost, and thus does not provide transportable non-volatile storage for user programs. However, this method does eliminate down-loading, and provides the user with a read/write memory medium for storing user programs so long as the permanent memory module is not removed from the data processing system and the battery backup remains intact.